1. Field of the Invention
The present invention relates to shoe sole construction, and more particularly, pertains to shoe soles or insoles that incorporate expandable or inflatable support cells.
2. Description of the Prior Art
Research has revealed that some foot complaints are caused by the reduced use of those leg and foot muscles that control compensatory action of the foot and ankle to variation in the plane or attitude of the surfaces encountered by the foot. These same muscles are additionally called upon to assist in pumping blood from the foot and leg back up to the heart. In fact, when a person stands perfectly still, and those muscles are not used, the venous pressure in the lower part of the legs can rise to the full hydrostatic value of about 110 to 130 cm of water in less than one minute. Under such circumstances, the pressure within the capillaries at the distal end of the lower extremities also increases greatly, and fluid flows into the tissue spaces. This, in addition to the capacitive enlargement of the veins of the legs, causes swelling and in as little as 15 minutes can diminish blood supply to the brain sufficiently to cause fainting. The pumping function is accomplished by the muscles with the cooperation of a multitude of one-way valves within veins located throughout the musculature of the leg and foot. Two to four such valves are typically found within each foot, while another 25 to 30 valves are normally disposed in veins within the extrinsic foot muscles in the leg below the knee. Contraction of such muscles proximate to a particular vein forces blood up past the next one-way valve which in turn prevents the blood's decent upon relaxation of those muscles. This comprises 70-80% of the mechanism by which blood is pumped from leg area back up to the heart.
Activity of these particular muscle groups therefore not only serves to alleviate some foot problems, but additionally controls veinous pressure to thereby enhance the body's overall blood circulation. The muscles are most readily exercised when successive steps taken while walking or successive stances assumed while standing cause each foot to assume a slightly different angular relation to the horizontal as compared with the previous position occupied thereby. This requisite angular variation is more readily achieved when the foot is caused to function on natural terrain, with its attendant irregularities and non-unformities, rather than on the flat, level, unyielding and unchanging surfaces typically encountered in an urban setting. The foot is after all well adapted to engage irregular surfaces due to the curved structure of the ball and heel while the city's concrete, asphalt and hardwood floors are more geared to accommodate wheeled traffic.
It has additionally been found that in order for the majority of these muscles to be best utilized, the variation in angular orientation of the foot should follow a random or pseudo-random sequence. Repeated short sequences are quickly learned and the body will tend to employ only a few favored muscles to compensate for variation in angular orientation when the successive orientations can be anticipated. Unpredicted or unexpected variation in orientation, as when the foot encounters natural or varied terrain causes all muscles to be used in a more properly balanced function.
The invention of U.S. Pat. No. 3,434,715, in which the inventor of the present invention is named as a coinventor, addresses this problem and describes a floor covering that provides the requisite variation in terrain for a person standing or walking thereon. The floor covering comprises a resilient support surface, which incorporates irregularly shaped and irregularly spaced areas of increased density. A person's foot supported thereby will assume slightly different angular orientations or attitudes depending on precisely where the foot encounters a particular area of increased density. Consequently walking there-across or standing thereon while shifting one's stance will result in the more balanced activity of the described muscle groups.
Shoe or orthotic design to date has not provided means to induce the proper activity of the described muscle groups. While various shoe sole systems have been disclosed that incorporate fluid-filled or inflatable cells, pumps and valving, traversal of flat and level terrain nonetheless results in predictable and unchanging placement of the foot with every step. The disclosed designs typically seek to cushion the loads a foot is subjected to while walking or running. Additionally, shoe sole structures are disclosed that provide for the ventilation of the shoe sole by pumping fluid through various cells to reduce temperatures. Some designs call for the circuiting of various fluids contained in the cells of the sole while others simply retard the intake or exhaust of air as weight is shifted about the sole.
Clearly, none of these prior art designs specifically induce nor even seek to induce activity of the muscle groups of the leg and foot responsible for compensation of the angular orientation of the foot.